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    SubjectRe: Using ftrace/perf as a basis for generic seccomp
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    On Wed, 2011-02-02 at 18:55 +0100, Ingo Molnar wrote:

    > The filter expression engine executes in the kernel, when the event happens. The
    > user-space perf tool parses the --filter parameter and passes it to the kernel as a
    > string in essence. The kerner parses this into atomic predicaments which are linked
    > to the event structure. When the event happens the predicaments are executed by the
    > filter engine.
    >
    > The expressions are simple, but rather flexible, so you can do 'fd==0||fd==1' and
    > more complex expressions, etc. The engine could also be extended.
    >
    > The kernel code is mostly in kernel/trace/trace_events_filter.c.
    >
    > I've Cc:-ed Tom, Frederic, Steve, Li Zefan and Arnaldo who have worked on the filter
    > engine, in case something is broken with this functionality or if there are other
    > questions :)

    Yep, and I'm currently working on them as well. As they currently have a
    32 pred limit (may seem like a lot, but I actually hit it). And I've
    also added short circuits (0 && .... no need to process more).

    I posted an RFC:

    https://lkml.org/lkml/2011/1/27/438

    and I'm again working on finishing it. Just a few more things to do. I
    got side tracked because my employer actually asked me to do something
    for them ;)

    -- Steve




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